If the geometry is given as Z-matrix, the default is to optimize the variables on which the Z-matrix depends. In case of xyz input, always all 3N coordinates are optimized, even if the xyz input depends on fewer variables. If Cartesian z-matrix input is used, optimization in full space is only enforced if automatic orientation is requested using the ORIENT, MASS, or CHARGE options in the geometry block. See opt_space in section 40.2.2 for details.